1. Field of the Invention
The present invention relates to a method of manufacturing an electron-emitting device, an electron source and an image-forming apparatus, and an apparatus of manufacturing the electron source.
2. Related Background Art
Two kinds of electron-emitting devices: a thermoelectron source and a cold cathode electron source are conventionally known. The types of the cold cathode electron source include a field emission type (hereinafter abbreviated as an FE type) electron-emitting device, a metal/insulating layer/metal type (hereinafter abbreviated as a MIM type) electron-emitting device, and a surface conduction electron-emitting device.
Known examples of the FE type are described by W. P. Dyke and W. W. Dolan in xe2x80x9cField emissionxe2x80x9d Advance in Electron Physics, 8, 89 (1956), by C. A. Spindt in xe2x80x9cPhysical Properties of thin-film field emission cathodes with molybdenum cones,xe2x80x9d J. Appl. Phys., 47, 5248 (1976), etc.
In contrast to this, known examples of the MIM type are described by C. A. Mead in xe2x80x9cOperation of Tunnel-Emission Devices,xe2x80x9d J. Apply. Phys. 32, 646 (1961) etc.
Examples of the surface conduction electron-emitting device are described by M. I. Elinson, Radio Eng. Electron Phys., 10, 1290, (1965), etc.
The surface conduction electron-emitting device utilizes a phenomenon in which electrons are emitted by flowing an electric current through a thin film of a small area formed on a substrate in parallel with a film face. Examples of this surface conduction electron-emitting device using an SnO2 thin film made by Elinson, etc. mentioned above, an Au thin film (G. Ditmmer, Thin Solid Films, 9, 317 (1972)), an In2O3/SnO2 thin film (M. Hartwell and C. G. Fonsted, IEEE Trans. ED Conf., 519 (1975)), a carbon thin film (Hisashi ARAKI, et al.: SHINKU (Vacuum), Vol. 26, No. 1, p. 22 (1983)), and the like have been reported.
The present applicant has made many proposals with respect to the surface conduction electron-emitting device having a novel construction and its application. For example, a basic construction and a manufacturing method of the surface conduction electron-emitting device, etc. are disclosed in Japanese Patent Application Laid-Open Nos. 7-235255 and 8-7749, etc. Main features of the above disclosure will next be explained briefly.
As schematically shown in FIG. 15A (a plan view) and FIG. 15B (a cross-sectional view), this surface conduction electron-emitting device is constructed by a pair of device electrodes 2, 3 opposed to each other on a substrate 1, and an electroconductive film 4 having a clearance 5a in one portion thereof and connected to the device electrodes. The clearance 5a is formed by a deposition film 6 deposited on the electroconductive film 4 and having carbon or a carbon compound as a main component. This electron-emitting device can emit electrons from a portion near the clearance 5a by applying a voltage between the device electrodes 2 and 3.
A conventional manufacturing method of the electron-emitting device will next be explained by using FIGS. 16A to 16D.
An electrode material is vacuum evaporated or sputtered to form a film on the substrate 1, and is patterned in a desirable shape by using a photolithography technique so that device electrodes 2, 3 are formed. An electroconductive film 4 is formed on the device electrodes 2, 3. Methods of vacuum evaporation, sputtering, CVD (chemical vapor deposition method), coating, etc. can be used in the formation of the electroconductive film 4.
Next, a voltage is applied between the device electrodes 2 and 3, and an electric current flows through the electroconductive film 4 so that a clearance 5 such as a crack, etc. is formed in one portion of the electroconductive film 4. This process is called a forming process.
An activation process is next performed. The activation process is a process for depositing carbon and/or a carbon compound 6 in the clearance 5 formed by the forming process. An emission current can be greatly increased by this activation process.
The activation process is conventionally performed by arranging an electron-emitting device within a vacuum container and highly evacuating the vacuum container and then applying a pulse voltage to the electron-emitting device after a lean organic substance gas is introduced. Thus, the organic substrate existing at a low partial pressure in the vacuum is decomposed and polymerized and is deposited in the vicinity of the clearance 5 as carbon and/or a carbon compound.
Next, a stabilization process is preferably performed. This stabilization process is a process for sufficiently removing molecules of the organic substance adsorbed to the electron-emitting device itself and its peripheral portion, or a wall face of the vacuum container for operating the electron-emitting device so that carbon and/or the carbon compound may not be further deposited even when the electron-emitting device is operated after this removal, thereby stabilizing characteristics of the electron-emitting device.
Such an electron-emitting device is simple in construction and is easily manufactured so that many electron-emitting devices can be arranged and formed in a large area. Therefore, an electron source of a large area can be formed by forming plural electron-emitting devices on the substrate and electrically connecting the electron-emitting devices to each other by wiring. An image-forming apparatus can be also formed by combining the above electron source and an image-forming member with each other.
A construction shown in FIG. 17 is widely known as the FE type electron-emitting device.
In FIG. 17, reference numerals 101, 102 and 103 respectively designate a substrate, a cathode electrode and an emitter. Reference numerals 105 and 104 respectively designate a gate electrode for emitting electrons from the emitter, and an insulating layer for electrically insulating the cathode electrode 102 and the gate electrode 105 from each other. There is also a case in which an electric current limiting resistance layer 106 is formed between the cathode electrode 102 and the emitter 103.
In the above FE type electron-emitting device, electrons are emitted from a tip of the emitter 103 when a voltage from several ten V to about several hundred V is applied between the cathode electrode 102 and the gate electrode 105. At this time, when an anode substrate is arranged above the electron-emitting device and an anode voltage of several kV is applied, the emitted electrons are trapped by the anode substrate.
The FE type electron-emitting device is variously considered to reduce the driving voltage and increase electron emitting efficiency. For example, the distance between the gate electrode and the emitter is reduced; a radius of curvature of the emitter is reduced; an emitter surface is covered with a low work function material, etc. Further, a technique for depositing a carbon compound on the emitter surface and improving the electron emitting efficiency by applying the voltage between the cathode electrode and the anode electrode in an atmosphere containing the organic substance is disclosed in recent years (Japanese Patent Application Laid-Open No. 10-50206).
In such an FE type electron-emitting device, the image-forming apparatus can be also formed by forming plural electron-emitting devices on the substrate and forming an electron source and combining the electron source with an image-forming member.
In the above activation process for depositing carbon or the carbon compound in conventional manufacturing methods of the electron-emitting device and the electron source, the organic substance existing at a low partial pressure in the vacuum is decomposed and polymerized and is deposited as carbon and/or the carbon compound. Therefore, it takes too much time to perform the activation process. Otherwise, more processing time is required to activate the electron source particularly having plural electron-emitting devices while a consuming speed of the organic substance consumed by the activation is increased with respect to a supply speed of the organic substance used in the activation. Accordingly, there is a case in which lack of the organic substance during the activation process causes no sufficient activation.
In particular, it is required in recent years that the image-forming apparatus to which the electron-emitting device is applied is large-sized. A large-sized image-forming apparatus will bring serious problems.
When the partial pressure of the organic substance used in the activation is increased, the above problem of the insufficiency of the supply of the organic substance is solved. However, when the activation is performed in the atmosphere having a high partial pressure of the organic substance, a problem exists in that no preferable electron-emitting characteristics are easily obtained.
An object of the present invention is to provide a method of manufacturing an electron-emitting device and an electron source capable of greatly shortening a time required for an activation process while preferable electron-emitting characteristics are obtained in the activation process in the method of manufacturing the electron-emitting device and the electron source.
Another object of the present invention is to provide a method and an apparatus of manufacturing the electron source in which the insufficiency of an organic substance during the activation process is solved to perform sufficient activation, and further to provide a method of manufacturing an image-forming apparatus using this electron source.
The present invention resides in a method of manufacturing an electron-emitting device, characterized by comprising a process for forming a pair of electric conductors spaced from each other on a substrate, and an activation process for forming a film of carbon or a carbon compound on at least one of the pair of electric conductors, wherein the activation process is sequentially performed within plural containers having different atmospheres.
Further, the present invention resides in a method of manufacturing an electron-emitting device, characterized by comprising a process for forming an electroconductive film on a substrate, including an electron-emitting region arranged between a pair of electrodes, and an activation process for forming a film of carbon or a carbon compound on the electroconductive film, wherein the activation process is sequentially performed within plural containers having different atmospheres.
Sill further, the present invention resides in a method of manufacturing an electron source, characterized by comprising a process for forming plural pairs of electric conductors each spaced from each other on a substrate, and an activation process for forming a film of carbon or a carbon compound on at lease one of each of the pairs of electric conductors, wherein the activation process is sequentially performed within plural containers having different atmospheres.
Still further, the present invention resides in a method of manufacturing an electron source, characterized by comprising a process for forming plural electroconductive films on a substrate, including an electron-emitting region arranged between a pair of electrodes, and an activation process for forming a film of carbon or a carbon compound on each of the electroconductive films, wherein the activation process is sequentially performed within plural containers having different atmospheres.
Still further, the present invention resides in an apparatus of manufacturing an electron source, comprising plural containers, means for exhausting each of the plural containers and means for introducing a gas into each of the containers, the exhausting and introducing means being arranged in each of the plural containers, and means for carrying a substrate on which the electron source is formed to/from each of the containers.
Still further, the present invention resides in a method of manufacturing an image-forming apparatus having an electron source and an image-forming member for forming an image by irradiating electrons from the electron source, wherein the electron source is manufactured by any one of the above manufacturing methods.